Coordinated ras-mediated induction of the metastatic phenotype and type IV collagenolytic activity was demonstrated previously (Thorgeirsson et al., Mol. Cell. Biol. 5: 259-262, 1985). For further characterization of the metalloproteinases involved, gelatin and type IV collagen sodium dodecyl sulfate (SDS) gel electrophoresis was used. The ras-transfected NIH/3T3 cells and malignant human cells expressed a 92 kDa metalloproteinase which was not detected in the untransfected control or normal human cells. Other gelatinolytic metalloproteinases (m.w. 68, 65 and 61kDa) were similarly expressed by the normal and malignant phenotype. HL-60 leukemia cells produced high levels of the 92 kDa proteinase, which was found to degrade both gelatin and type IV collagen when analyzed by SDS gel electrophoresis with substrates copolymerized into the acrylamide. These results suggest that the 92 kDa gelatin-type IV collagen degrading metalloproteinase plays an important role in tumor cell invasion.